Design study on differential die-away technique in an integrated active neutron NDA system for non-nuclear proliferation

A specific Differential Die-away Analysis (DDA) system in an advanced non-destructive analysis (NDA) system using a compact pulsed neutron generator has been studied and designed for non-nuclear proliferation in the Japan Atomic Energy Agency (JAEA). The NDA system is composed mainly of combination of four active neutron analysis techniques, DDA, PGA (Prompt Gamma-ray Analysis), NRTA (Neutron Resonance Transmission Analysis) and DGS (Delayed Gamma Spectroscopy). The design study on the DDA section in the system has been performed with Monte Carlo simulation code (MCNP) to evaluate the performance of the DDA system. The simulation result shows that the
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Pu mass (contained in MOX fuel) of as low as 0.01 g is detectable. The dependence of the performance on the type of the inner wall material in the DDA section and the thickness of the cylindrical moderator placed to circumscribe the measurement sample are presented.